The module (MicroSD Card Adapter) is a Micro SD card reader module, and the SPI interface via the file system driver, microcontroller system to complete the MicroSD card read and write files.
Arduino users can directly use the Arduino IDE comes with an SD card to complete the library card initialization and read-write

Level conversion circuit:
Micro SD card into the direction of signals into 3.3V, MicroSD card toward the direction of the control interface MISO signal is also converted to 3.3V, general AVR microcontroller system can read the signal